Mini Madness

This is at track Carpet in Children room, you have to use a Satellite power up near the end of a lap at the core.

Once you complete 4 championships, the 5th championship is Children's Room. Load up challenge mode to get this achievement. The power up you need Is white or grey and it's called transmitter. At the very end of your 1st lap before you go down to the floor you'll be on the green slide where you see power-ups. If you don't see the white or grey power-up just collect all 3 and circle back and it should eventually pop up. The gravity core is just after the 1st lap it'll be technically the second lap. Once you drive near the gravity core a line will pop up showing that it is possible to use. Press X and the achievement will pop!